Without an example of your input file this is my best guess

#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my @colname = ("2:", "6:", "4:", "3:");

my $datafile = 'datafile2.txt';#$ARGV[0];
open my $fh,'<',$datafile 
     or die "Could not open $datafile : $!";

# column header line
my @header = split /\s+/,<$fh>;
chomp(@header);
#print Dumper \@header;

# convert name to colno
my %colno = ();
for my $i (0..$#header){
  my ($name,$val) = split ':',$header[$i];
  $colno{ $name.':' } = $i;
}
#print Dumper \%colno;

# array of required columns
my @colno = map { $colno{$_} } @colname;
#print Dumper \@colno;

# process datalines
seek $fh,0,0;
while (<$fh>){
  chomp;
  my @f = split /\s+/,$_;
  print join "\t",@f[@colno];
  print "\n";
}
close $fh;

__DATA__
0 2:-0.5795 3:0.33582025 4:55.8255 5:65.316997 6:15 7:16 8:57 9:28 10:
+29 11:23 12:5
1 2:-1.4034 3:1.96953156 4:53.4424 5:65.316997 6:15 7:16 8:57 9:28 10:
+29 11:23 12:5
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